Recently, in the light of resources saving, energy saving and in addition, protection of environment, a strong demand for reduction of exhausted carbon dioxide is increasing, and various countermeasures such as weight saving of a vehicle and use of electric energy have been considered. Accordingly, it is demanded to enhance fuel efficiency by decreasing rolling resistance of a tire for a vehicle, and also improvement of performances such as durability is desired.
For example, there are known, as a method for decreasing rolling resistance, techniques such as blending of silica, decrease in an amount of a filler, use of a filler having less reinforcing property. However, there is a tendency that a mechanical strength of a rubber decreases and various performances are degraded.
In JP 2009-120819 A, use of a silane coupling agent having a highly reactive mercapto group (mercapto silane coupling agent) for the purpose of improving performance such as fuel efficiency has been considered. However, in a mercapto silane coupling agent, good fuel efficiency, wet grip performance and abrasion resistance are obtained while since the mercapto silane coupling agent has high reactivity, there is a concern that gelation occurs during kneading with a rubber component and processability is lowered.
Meanwhile, JP 2014-047327 A describes that processability of a rubber composition, fuel efficiency, rubber strength, abrasion resistance and crack growth resistance are improved in good balance by further blending a specific polysulfide compound to a rubber composition comprising a silane coupling agent having a mercapto group.